$ { \left[\begin{array}{rr}{-2} & {-2} \\ {2} & {3}\end{array}\right]+\left[\begin{array}{rr}{3} & {-1} \\ {-1} & {-1}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{-2}+{3} & {-2}+{-1} \\ {2}+{-1} & {3}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{1} & {-3} \\ {1} & {2}\end{array}\right]}$